• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.4
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• pp.133-142
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• 1983

A new dynamic pile-driving formula derived by the writer, in which the mechanics of stress waves and the effect of residual stresses were considered for more accurate prediction of the load carrying capacity of piles, was compared with other representative formulas through statistical analysis using the load test results. As the result, the new formula was estimated as highly accurate and reliable, with its safety factor less than 3.

• 한국도로학회:학술대회논문집
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• 2006.10a
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• pp.211-216
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• 2006

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1152-1158
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• 2007

Although various fast and simple, testing devices have been developed in many countries such as the U.S, Japan, and European countries, these testing devices are not commonly used in Korea. In this study, compaction fur the field density test was carried out with a hand-guided vibrating roller. The results of the field density test were compared with those of the new testing devices such as the geogauge, soil impact hammer(CASPFOL), light falling weight deflectometer(LFWD), dynamic cone penetration(DCP). Regression analyses were conducted with the data from new testing devices. The analysis results showed that the correlation coefficients were high in the range of $70{\sim}95%$.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.582-588
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• 2007

Since the turnout system in railroad restricts the train speed, the KNR (Korean National Railroad) provides the specification for the speed (130km/h) of the train when the train passes the turnout system. Therefore, the turnout system in pre-existing railroad is necessary to be improved to speed-up for the train. In this study, the dynamic wheel-load field tests have been performed to evaluate the track performance and the roadbed bearing capacity has been examined using numerical analysis at the turnout crossing in the conventional and improved turnout system. The impact factor is estimated using the data sets achieved from the dynamic wheel-load field tests in the conventional and improved turnout system. The stress acting on the roadbed for the improved turnout system is substantially decreased compare to that for the conventional turnout system.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.45-58
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• 2015

Even though the plate bearing test (PBT) to evaluate the load baring capacity and the field density test to evaluate the relative density are mainly used for quality control of soil compaction in Korea, use of the dynamic cone penetrometer test (DCPT) and the dynamic plate bearing test (DPBT) considering economic feasibility, rapidity, and suitability for field conditions increase to use for quality control of soil compaction. In this study, bearing capacity and relative density of subgrade with thickness of 20 cm, 30 cm, and 40 cm are estimated using PBT, DCPT, DPBT and field density test in three field compaction tests, and the relationship among various compaction evaluation methods is analyzed and discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.435-444
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• 2006

This paper investigates the effect of 3-dimensional FE models to evaluation results of jointed concrete pavements which is back-calculated by AREA method. Sensitivity of 3-dimensional FE models developed to simulate the behavior of real jointed concrete pavement are analyzed after compared with 2-dimensional FE models using ILLISLAB. In comparison with 2-dimensional models, influence of concrete contraction under loading plate and base layer on surface deflections is more than that of loading configuration. Deflections at 3-dimensional model between linear and nonlinear temperature distribution under same temperature difference are similar, but noticeable differences are investigated in low elastic modulus of foundations. Dynamic deflections under loading plate are larger than static deflections in high elastic modulus of foundation, but smaller in low elastic modulus. Lower dynamic modulus of subgrade reactions are backcalculated by dynamic deflections than by static deflections. But reverse trend is investigated in the backcalculated elastic modulus of concrete which describes trends of the field backcalculation values calculated from AREA method.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.17-26
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• 2004

The in-situ California Bearing Ratio (CBR) test has been widely used for evaluating the subgrade condition in asphalt concrete pavements. However, because the in-situ CBR test is expensive and takes plenty of time for operation, it is very difficult to figure out the in-situ characteristics of subgrade strength in detail. For faster and economical operation, the Dynamic Cone Penetrometer (DCP) has been often utilized for estimating the subgrade strength in the field. The relationship between the CBR value and DCP index obtained from the DCP testing has been studied using the laboratory and in-situ testing by other foreign researchers. The objective of this study is to determine the relationship between in-situ CBR value and DCP index of the subgrade materials used in Korea. The DCP index for evaluating the strength of subgrade materials produced in Korea is presented in this paper. Research results propose the regression equation to explain the relationship between the CBR and DCP tests. The in-situ CBR values of subgrade materials range from 20 to 45% indicating the good and sound subgrade condition.

• Geotechnical Engineering
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• v.13 no.5
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• pp.145-154
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• 1997

Though the static pile load tests gives the mosts accurate estimation on the load carrying capacity of tested pile, it appears time-consuming and not economical. Many test methods using equipments, such as Pile Driving Analyzer(PDA), STATNAMIC, and Osterberg cell, have been introduced in Korea, and pile best using PDA has been gaining popularity because of iris fast and simple operation. Static and dynamic tests results on the piles installed in the granular coils were analyzed to investigate the effect of geometrical damping on the estimated load carrying capacity. It was found that the CAPWAP analysis without considering geometrical damping effect underestimates the pile capacity by 30~60% under certain conditions. It was observed that the underestimation of pile capacity by CAPWAP occurs on the piles installed in the water-borne granular boils by SIP methods. When Smith skin damping value(SSkn) greater than 1.0 sec/m is obtained in CAPWAP analysis, it may reflect the large possibility of underestimation of pile capacity. The introduction of the geometircal damping option in CAPWAP analysis gives reasonable pile capacity, compared with the static pile load test results, and reduces the SSb value under 0.7 sec/m.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.5
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• pp.749-760
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• 2017

Recently, the proportion of tunnel structures in roads and railways has increased rapidly. Along with this trend, the rate of occurrence of cracks and dropouts in concrete lining of tunnel structures is increasing. Generally, maintenance of such concrete lining is normalized and managed as the core of maintenance work in tunnel maintenance. However, the maintenance of the tunnel pavement is important in securing driver in the tunnel. In the design of tunnels, the underground condition of the tunnel is designed to be in good rock condition, so there have not been many cases of cracks in the tunnel pavement in the past. Recently, the construction of tunnel structures has been rapidly increased, and the length of the tunnels has become longer.Tunnel pavement installed in these ground conditions is increasing the occurrence of cracks in the pavement due to decrease of bearing capacity of the pavement after a long time. In this study, FWD and GPR were conducted to analyze the types of cracks and the reduction of bearing capacity in the tunnel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.927-935
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• 2011

In-situ California Bearing Ratio(CBR) test has been widely used for evaluating the subgrade condition in pavements. However, because the in-situ CBR test is expensive and takes time for operation, it is difficult to figure out the in-situ characteristics of subgrade strength in detail. For faster and economical operation, the Dynamic Cone Penetrometer(DCP) has been often utilized for estimating the subgrade strength in the field. The purpose of this paper is to determine the relationship between CBR value and DCP index of the embankment constructed with mixtures of soil and waste lime. Waste lime used in this study is producted as a by-product in the manufacturing process of making $Na_2CO_3$ from local chemical factory in Incheon. In this field measurement, the geotechnical tests such as field water content, field density, field CBR test, and dynamic cone penetration test were conducted.